parent dns answers the ARR of child dns

[Chris Buxton]

On Dec 3, 2009, at 3:38 AM, Tech W. wrote:
> # dig smartip.gduf.edu.cn ns +short
> dtone1.gduf.edu.cn.
> 
> # dig www.smartip.gduf.edu.cn  +short
> 121.8.235.88
> 
> # dig www.smartip.gduf.edu.cn +trace 

[...]

> www.smartip.gduf.edu.cn. 8      IN      A       218.192.12.4
> www.smartip.gduf.edu.cn. 8      IN      A       218.192.12.10
> www.smartip.gduf.edu.cn. 8      IN      A       218.192.12.3
> ;; Received 89 bytes from 218.192.12.6#53(DNS.gduf.edu.cn) in 106 ms

DNS.gduf.edu.cn is open to recursive queries from anyone. Is it possible you were seeing a cached answer?

A DNS server that is authoritative for a zone that has subzones that are delegated to other DNS servers should not be performing recursion. Not for anyone. It leads to confusing results.

$ dig www.smartip.gduf.edu.cn +norec @DNS.gduf.edu.cn

; <<>> DiG 9.6.0-APPLE-P2 <<>> www.smartip.gduf.edu.cn +norec @DNS.gduf.edu.cn
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22315
;; flags: qr ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;www.smartip.gduf.edu.cn.	IN	A

;; AUTHORITY SECTION:
smartip.gduf.edu.cn.	3600	IN	NS	dtone1.gduf.edu.cn.

;; ADDITIONAL SECTION:
dtone1.gduf.edu.cn.	3600	IN	A	218.192.12.233

;; Query time: 398 msec
;; SERVER: 218.192.12.6#53(218.192.12.6)
;; WHEN: Thu Dec  3 08:43:50 2009
;; MSG SIZE  rcvd: 97

$ dig www.smartip.gduf.edu.cn +norec @dtone1.gduf.edu.cn

; <<>> DiG 9.6.0-APPLE-P2 <<>> www.smartip.gduf.edu.cn +norec @dtone1.gduf.edu.cn
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47739
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;www.smartip.gduf.edu.cn.	IN	A

;; ANSWER SECTION:
www.smartip.gduf.edu.cn. 30	IN	A	121.8.235.88

;; AUTHORITY SECTION:
smartip.gduf.edu.cn.	3600	IN	NS	dtone1.gduf.edu.cn.

;; Query time: 396 msec
;; SERVER: 218.192.12.233#53(218.192.12.233)
;; WHEN: Thu Dec  3 08:44:17 2009
;; MSG SIZE  rcvd: 78

Chris Buxton
Professional Services
Men & Mice